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Jet pumpJet pump description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080310970, Jet pump. Brief Patent Description - Full Patent Description - Patent Application Claims
This invention relates to a method and apparatus for moving a fluid. The present invention has reference to improvements to a fluid mover having a number of practical applications of diverse nature ranging from marine propulsion systems to pumping applications for moving and/or mixing fluids and/or solids of the same or different characteristics. The present invention also has relevance in the fields inter alia of heating, cooking, cleaning, aeration, gas fluidisation, and agitation of fluids and fluids/solids mixtures, particle separation, classification, disintegration, mixing, emulsification, homogenisation, dispersion, maceration, hydration, atomisation, droplet production, viscosity reduction, dilution, shear thinning, transport of thixotropic fluids and pasteurisation. More particularly the invention is concerned with the provision of an improved fluid mover having essentially no moving parts. Ejectors are well known in the art for moving working or process fluids by the use of either a central or an annular jet which emits steam into a duct in order to move the fluids through or out of appropriate ducting or into or through another body of fluid. The ejector principally operates on the basis of inducing flow by creating negative pressure, generally by the use of the venturi principle. The majority of these systems utilise a central steam nozzle where the induced fluid generally enters the duct orthogonally to the axis of the jet, although there are exceptions where the reverse arrangement is provided. The steam jet is accelerated through an expansion nozzle into a mixing chamber where it impinges on and is mixed with working fluid. The mixture of working fluid and steam is accelerated to higher velocities within a downstream convergent section prior to a divergent section, e.g. a venturi. The pressure gradient generated in the venturi induces new working fluid to enter the mixing chamber. The energy transfer mechanism in most steam ejector systems is a combination of momentum, heat and mass transfer but by varying proportions. Many of these systems employ the momentum transfer associated with a converging flow, while others involve the generation of a shock wave in the divergent section. One of the major limitations of the conventional convergent/divergent systems is that their performance is very sensitive to the position of the shock wave which tends to be unstable, easily moving away from its optimum position. It is known that if the shock wave develops in the wrong place within the convergent/divergent sections, the relevant unit may well stall. Such systems can also only achieve a shock wave across a restricted section. Furthermore, for systems which employ a central steam nozzle, the throat dimension restriction and the sharp change of direction affecting the working fluid presents a serious limitation on the size of any particulate throughput and certainly any rogue material that might enter the system could cause blockage. An improved fluid mover is described in our International Patent Application No PCT/GB2003/004400 in which the interaction of a working fluid or fluids and a transport fluid projected from a nozzle arrangement provides pumping, entrainment, mixing, heating, emulsification, and homogenization etc. of the working fluid or fluids. The fluid mover introduces an annular supersonic jet of transport fluid, typically steam, into a relatively large diameter straight through hollow passage. Through a combination of momentum transfer, high shear, and the generation of a condensation shock wave, the high velocity steam induces and acts upon the working fluid passing through the centre of the hollow body. PCT/GB2003/004400 describes that the transport fluid is preferably a condensable fluid and may be a gas or vapour, for example steam, which may be introduced in either a continuous or discontinuous manner. At or near the point of introduction of the transport fluid, for example immediately downstream thereof, a pseudo-vena contracta or pseudo convergent/divergent section is generated, akin to the convergent/divergent section of conventional steam ejectors but without the physical constraints associated therewith since the relevant section is formed by the effect of the steam impacting upon the working or process fluid. Accordingly the fluid mover is more versatile than conventional ejectors by virtue of a flexible fluidic internal boundary described by the pseudo-vena contracta. The flexible boundary lies between the working fluid at the centre and the solid wall of the unit, and allows disturbances or pressure fluctuations in the multi phase flow to be accommodated better than for a solid wall. This advantageously reduces the supersonic velocity within the multi phase flow, resulting in better droplet dispersion, increasing the momentum transfer zone length, thus producing a more intense condensation shock wave. PCT/GB2003/004400 further discloses that the positioning and intensity of the shock wave is variable and controllable depending upon the specific requirements of the system in which the fluid mover is disposed. The mechanism relies on a combination of effects in order to achieve its high versatility and performance, notably heat, momentum and mass transfer which gives rise to the generation of the shock wave and also provides for shearing of the working fluid flow on a continuous basis by shear dispersion and/or dissociation. Preferably the nozzle is located as close as possible to the projected surface of the working fluid in practice and in this respect a knife edge separation between the transport fluid or steam and the working fluid stream is of advantage in order to achieve the requisite degree of interaction. The angular orientation of the nozzle with respect to the working fluid stream is of importance and may be shallow. Further, PCT/GB2003/004400 discloses that the or each transport fluid nozzle may be of a convergent-divergent geometry internally thereof, and in practice the nozzle is configured to give the supersonic flow of transport fluid within the passage. For a given steam condition, i.e. dryness, pressure and temperature, the nozzle is preferably configured to provide the highest velocity steam jet, the lowest total pressure drop and the highest static enthalpy between the steam chamber and the nozzle exit. The nozzle is preferably configured to avoid any shock in the nozzle itself. For example only, and not by way of limitation, an optimum area ratio for the nozzle, namely exit area: throat area, lies in the range 1.75 and 7.5, with an included angle of less than 9°. The or each nozzle is conveniently angled towards the working fluid flow and also faces generally towards the cutlet of the fluid mover. This helps penetration of the working fluid by the transport fluid, which may help shear or thermal dispersion of the working fluid. This may also prevent both kinetic energy dissipation on the wall of the passage and premature condensation of the steam at the wall of the passage, where an adverse temperature differential prevails. The angular orientation of the nozzles is selected for optimum performance which is dependent inter alia on the nozzle orientation and the internal geometry of the mixing chamber. Further the angular orientation of the or each nozzle is selected to control the pseudo-convergent/divergent profile, the pressure profile within the mixing chamber, the enthalpy addition and the condensation shock wave intensity or position in accordance with the pressure and flow rates required from the fluid mover. Moreover, the creation of turbulence, governed inter alia by the angular orientation of the nozzle, is important to achieve optimum performance by dispersal of the working fluid to a vapour-droplet phase in order to increase acceleration by momentum transfer. This aspect is of particular importance when the fluid mover is employed as a pump. For example, and not by way of limitation, in the present invention it has been found that an angular orientation for the or each nozzle may lie in the range 0 to 30° with respect to the flow direction of the working fluid. A series of nozzles with respective mixing chamber sections associated therewith may be provided longitudinally of the passage and in this instance the nozzles may have different angular orientations, for example decreasing from the first nozzle in a downstream direction. Each nozzle may have a different function from the other or others, for example pumping, mixing, disintegrating, and may be selectively brought into operation in practice. Each nozzle may be configured to give the desired effects upon the working fluid. Further, in a multi-nozzle system by the introduction of the transport fluid, for example steam, phased heating may be achieved. This approach may be desirable to provide a gradual heating of the working fluid. An object of the present invention is to improve the performance of the fluid mover by enhancing the energy transfer mechanism between the high velocity transport fluid and the working fluid. This improves the performance of the fluid mover having essentially no moving parts having an improved performance than fluid movers currently available in the absence of any constriction such as is exemplified in the prior art recited in the aforementioned patent. According to a first aspect of the present invention a fluid mover includes a hollow body provided with a straight-through passage of substantially constant cross section with an inlet at one end of the passage and an outlet at the other end of the passage for the entry and discharge respectively of a working fluid, a nozzle substantially circumscribing and opening into said passage intermediate the inlet and outlet ends thereof, an inlet communicating with the nozzle for the introduction of a transport fluid, a mixing chamber being formed within the passage downstream of the nozzle, the nozzle internal geometry and the bore profile immediately upstream of the nozzle exit being so disposed and configured to optimise the energy transfer between the transport fluid and working fluid that in use through the introduction of transport fluid the working fluid or fluids are atomised to form a dispersed vapour/droplet flow regime with locally supersonic flow conditions within a pseudo-vena contracta, resulting in the creation of a supersonic condensation shock wave within the downstream mixing chamber by the condensation of the transport fluid. The transport fluid is preferably a condensable fluid and may be a gas or vapour, for example steam, which may be introduced in either a continuous or discontinuous manner. According to a second aspect of the present invention a fluid mover of the kind described in our aforementioned patent application, includes a hollow body provided with a straight-through passage of substantially constant cross section with an inlet at one end of the passage and an outlet at the other end of the passage for the entry and discharge respectively of a working fluid, a nozzle substantially circumscribing and opening into said passage intermediate the inlet and outlet ends thereof, an inlet communicating with the nozzle for the introduction of steam, a mixing chamber being formed within the passage downstream of the nozzle, the nozzle internal geometry and the bore profile immediately upstream of the nozzle exit being so disposed and configured to optimise the energy transfer between the steam and working fluid that in use through the introduction of steam the working fluid or fluids are atomised to form a dispersed vapour/droplet flow regime with locally supersonic flow conditions within a pseudo-vena contracta, resulting in the creation of a supersonic condensation shock wave within the downstream mixing chamber by the condensation of the steam. The nozzle may be of a form to correspond with the shape of the passage and thus for example a circular passage would advantageously be provided with an annular nozzle circumscribing it. The term ‘annular’ as used herein is deemed to embrace any configuration of nozzle or nozzles that circumscribes the passage of the fluid mover, and encompasses circular, irregular, polygonal and rectilinear shapes of nozzle. The term “circumscribing” or “circumscribes” as used herein is deemed to embrace not only a continuous nozzle surrounding the passage, but also a discontinuous nozzle having two or more nozzle outlets partially or entirely surrounding the passage. The or each nozzle may be of a convergent-divergent geometry internally thereof, and in practice the nozzle is configured to give the supersonic flow of transport fluid within the passage. For a given, steam condition, i.e. dryness, pressure and temperature, the nozzle is preferably configured to provide the highest velocity steam jet, the lowest total pressure drop and the highest enthalpy between the steam chamber and nozzle exit. The condensation profile in the mixing chamber determines the expansion ratio profile across the nozzle. With relatively low working fluid temperatures condensation is dominant, and the exit pressure of the transport fluid nozzle is low. The exit pressure of the transport fluid nozzle is higher when the bulk temperature of the working fluid is higher. According to a third aspect of the present invention a method of moving a working fluid includes
presenting a fluid mover to the working fluid, the mover having a straight-through passage of substantially constant cross section,
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